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Zero-Drift, Single-Supply, Rail-to-Rail Input/Output Operational Amplifier AD8628/AD8629/AD8630
FEATURES
Lowest auto-zero amplifier noise Low offset voltage: 1 V Input offset drift: 0.002 V/C Rail-to-rail input and output swing 5 V single-supply operation High gain, CMRR, and PSRR: 120 dB Very low input bias current: 100 pA max Low supply current: 1.0 mA Overload recovery time: 10 s No external components required
PIN CONFIGURATIONS
OUT 1 V- 2 +IN 3
AD8628
TOP VIEW (Not to Scale)
5
V+
4
-IN
Figure 1. 5-Lead TSOT (UJ-5) and 5-Lead SOT-23 (RT-5)
NC 1 -IN 2 +IN 3
8
NC V+
AD8628
7
Figure 3. 8-Lead SOIC_N (R-8)
OUT A 1 -IN A 2 +IN A 3 V- 4
8
V+ OUT B
02735-064
02735-065
02735-066
AD8629
TOP VIEW (Not to Scale)
7 6 5
-IN B +IN B
Figure 4. 8-Lead MSOP (RM-8)
OUT A -IN A +IN A V+ +IN B -IN B OUT B
1 2 3 4 5 6 7 14 13
OUT D -IN D +IN D V- +IN C -IN C OUT C
AD8630
TOP VIEW (Not to Scale)
12 11 10 9 8
Figure 5. 14-Lead SOIC_N (R-14)
OUT A 1 -IN A 2 +IN A 3 V+ 4
14 OUT D 13 -IN D
AD8630
12 +IN D
TOP VIEW 11 V- (Not to Scale) +IN B 5 10 +IN C -IN B 6 OUT B 7
9 8
-IN C OUT C
Figure 6. 14-Lead TSSOP (RU-14)
Rev. E
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 (c) 2005 Analog Devices, Inc. All rights reserved.
02735-063
Automotive sensors Pressure and position sensors Strain gage amplifiers Medical instrumentation Thermocouple amplifiers Precision current sensing Photodiode amplifier
NC = NO CONNECT
Figure 2. 8-Lead SOIC_N (R-8)
OUT A 1 -IN A 2 +IN A 3
8
V+ OUT B
AD8629
7
6 -IN B TOP VIEW V- 4 (Not to Scale) 5 +IN B
02735-002
APPLICATIONS
6 OUT TOP VIEW V- 4 (Not to Scale) 5 NC
02735-001
AD8628/AD8629/AD8630 TABLE OF CONTENTS
General Description ......................................................................... 3 Specifications..................................................................................... 4 Electrical Characteristics--Vs = 5.0 V............................................. 4 Electrical Characteristics--Vs = 2.7 V............................................. 5 Absolute Maximum Ratings............................................................ 6 ESD Caution.................................................................................. 6 Typical Performance Characteristics ............................................. 7 Functional Description .................................................................. 15 1/f Noise....................................................................................... 15 Peak-to-Peak Noise .................................................................... 16 Noise Behavior with First-Order Low-Pass Filter.................. 16 Total Integrated Input-Referred Noise for First-Order Filter.................................................................. 16 Input Overvoltage Protection ................................................... 17 Output Phase Reversal............................................................... 17 Overload Recovery Time .......................................................... 17 Infrared Sensors.......................................................................... 18 Precision Current Shunt Sensor ............................................... 19 Output Amplifier for High Precision DACs........................... 19 Outline Dimensions ....................................................................... 20 Ordering Guide .......................................................................... 22
REVISION HISTORY
5/05--Rev. D to Rev. E Changes to Ordering Guide .......................................................... 22 1/05--Rev. C to Rev. D Added AD8630 ...................................................................Universal Added Figure 5 and Figure 6........................................................... 1 Changes to Caption in Figure 8 and Figure 9 ............................... 7 Changes to Caption in Figure 14 .................................................... 8 Changes to Figure 17........................................................................ 8 Changes to Figure 23 and Figure 24............................................... 9 Changes to Figure 25 and Figure 26............................................. 10 Changes to Figure 31...................................................................... 11 Changes to Figure 40, Figure 41, Figure 42................................. 12 Changes to Figure 43 and Figure 44............................................. 13 Changes to Figure 51...................................................................... 15 Updated Outline Dimensions ....................................................... 20 Changes to Ordering Guide .......................................................... 22 10/04--Rev. B to Rev. C Updated Formatting ...........................................................Universal Added AD8629 ...................................................................Universal Added SOIC and MSOP Pin Configurations ............................... 1 Added Figure 48.............................................................................. 13 Changes to Figure 62...................................................................... 17 Added MSOP Package ................................................................... 19 Changes to Ordering Guide .......................................................... 22 10/03--Rev. A to Rev. B Changes to General Description .....................................................1 Changes to Absolute Maximum Ratings........................................4 Changes to Ordering Guide .............................................................4 Added TSOT-23 Package .............................................................. 15 6/03--Rev. 0 to Rev. A Changes to Specifications.................................................................3 Changes to Ordering Guide .............................................................4 Change to Functional Description............................................... 10 Updated Outline Dimensions....................................................... 15 10/02--Revision 0: Initial Version
Rev. E | Page 2 of 24
AD8628/AD8629/AD8630 GENERAL DESCRIPTION
This amplifier has ultralow offset, drift, and bias current. The AD8628/AD8629/AD8630 are wide bandwidth auto-zero amplifiers featuring rail-to-rail input and output swings and low noise. Operation is fully specified from 2.7 V to 5 V single supply (1.35 V to 2.5 V dual supply). The AD8628/AD8629/AD8630 provide benefits previously found only in expensive auto-zeroing or chopper-stabilized amplifiers. Using Analog Devices' topology, these zero-drift amplifiers combine low cost with high accuracy and low noise. No external capacitor is required. In addition, the AD8628/ AD8629/AD8630 greatly reduce the digital switching noise found in most chopper-stabilized amplifiers. With an offset voltage of only 1 V, drift of less than 0.005 V/C, and noise of only 0.5 V p-p (0 Hz to 10 Hz), the AD8628/AD8629/AD8630 are suited for applications in which error sources cannot be tolerated. Position and pressure sensors, medical equipment, and strain gage amplifiers benefit greatly from nearly zero drift over their operating temperature range. Many systems can take advantage of the rail-to-rail input and output swings provided by the AD8628/AD8629/AD8630 to reduce input biasing complexity and maximize SNR. The AD8628/AD8629/AD8630 are specified for the extended industrial temperature range (-40C to +125C). The AD8628 is available in tiny TSOT-23, SOT-23, and the 8-lead narrow SOIC plastic packages. The AD8629 is available in the standard 8-lead narrow SOIC and MSOP plastic packages. The AD8630 quad amplifier is available in 14-lead narrow SOIC and TSSOP plastic packages.
Rev. E | Page 3 of 24
AD8628/AD8629/AD8630 SPECIFICATIONS
ELECTRICAL CHARACTERISTICS--VS = 5.0 V
VS = 5.0 V, VCM = 2.5 V, TA = 25C, unless otherwise noted. Table 1.
Parameter INPUT CHARACTERISTICS Offset Voltage Input Bias Current (AD8630) Input Offset Current Input Voltage Range Common-Mode Rejection Ratio Large Signal Voltage Gain 1 Offset Voltage Drift OUTPUT CHARACTERISTICS Output Voltage High Symbol VOS -40C TA +125C IB -40C TA +125C IOS -40C TA +125C CMRR AVO VOS/T VOH VCM = 0 V to 5 V -40C TA +125C RL = 10 k, VO = 0.3 V to 4.7 V -40C TA +125C -40C TA +125C RL = 100 k to ground -40C TA +125C RL = 10 k to ground -40C TA +125C RL = 100 k to V+ -40C TA +125C RL = 10 k to V+ -40C TA +125C -40C TA +125C Output Current POWER SUPPLY Power Supply Rejection Ratio Supply Current/Amplifier INPUT CAPACITANCE Differential Common-Mode DYNAMIC PERFORMANCE Slew Rate Overload Recovery Time Gain Bandwidth Product NOISE PERFORMANCE Voltage Noise Voltage Noise Density Current Noise Density
1
Conditions
Min
Typ 1 30 100 50
Max 5 10 100 300 1.5 200 250 5
Unit V V pA pA nA pA pA V dB dB dB dB V/C V V V V mV mV mV mV mA mA mA mA
0 120 115 125 120
140 130 145 135 0.002 4.996 4.995 4.98 4.97 1 2 10 15 50 40 30 15
0.02
4.99 4.99 4.95 4.95
Output Voltage Low
VOL
5 5 20 20
Short-Circuit Limit
ISC IO -40C TA +125C PSRR ISY VS = 2.7 V to 5.5 V -40C TA +125C VO = 0 V -40C TA +125C
25
115
130 0.85 1.0 1.5 8.0
1.1 1.2
dB mA mA pF pF V/s ms MHz V p-p V p-p nV/Hz fA/Hz
CIN
SR GBP en p-p en p-p en in
RL = 10 k
1.0 0.05 2.5 0.5 0.16 22 5
0.1 Hz to 10 Hz 0.1 Hz to 1.0 Hz f = 1 kHz f = 10 Hz
Gain testing is highly dependent on test bandwidth.
Rev. E | Page 4 of 24
AD8628/AD8629/AD8630
ELECTRICAL CHARACTERISTICS--VS = 2.7 V
VS = 2.7 V, VCM = 1.35 V, VO = 1.4 V, TA = 25C, unless otherwise noted. Table 2.
Parameter INPUT CHARACTERISTICS Offset Voltage Input Bias Current (AD8630) Input Offset Current Input Voltage Range Common-Mode Rejection Ratio Large Signal Voltage Gain 1 Offset Voltage Drift OUTPUT CHARACTERISTICS Output Voltage High Symbol VOS -40C TA +125C IB -40C TA +125C IOS -40C TA +125C CMRR AVO VOS/T VOH VCM = 0 V to 2.7 V -40C TA +125C RL = 10 k, VO = 0.3 V to 2.4 V -40C TA +125C -40C TA +125C RL = 100 k to ground -40C TA +125C RL = 10 k to ground -40C TA +125C RL = 100 k to V+ -40C TA +125C RL = 10 k to V+ -40C TA +125C -40C TA +125C Output Current POWER SUPPLY Power Supply Rejection Ratio Supply Current/Amplifier INPUT CAPACITANCE Differential Common-Mode DYNAMIC PERFORMANCE Slew Rate Overload Recovery Time Gain Bandwidth Product NOISE PERFORMANCE Voltage Noise Voltage Noise Density Current Noise Density
1
Conditions
Min
Typ 1 30 100 1.0 50
Max 5 10 100 300 1.5 200 250 2.7
Unit V V pA pA nA pA pA V dB dB dB dB V/C V V V V mV mV mV mV mA mA mA mA
0 115 110 110 105
130 120 140 130 0.002 2.695 2.695 2.68 2.675 1 2 10 15 15 10 10 5
0.02
2.68 2.68 2.67 2.67
Output Voltage Low
VOL
5 5 20 20
Short-Circuit Limit
ISC IO -40C TA +125C PSRR ISY VS = 2.7 V to 5.5 V -40C TA +125C VO = 0 V -40C TA +125C
10
115
130 0.75 0.9 1.5 8.0
1.0 1.2
dB mA mA pF pF V/s ms MHz V p-p nV/Hz fA/Hz
CIN
SR GBP en p-p en in
RL = 10 k
1 0.05 2 0.5 22 5
0.1 Hz to 10 Hz f = 1 kHz f = 10 Hz
Gain testing is highly dependent on test bandwidth.
Rev. E | Page 5 of 24
AD8628/AD8629/AD8630 ABSOLUTE MAXIMUM RATINGS
Table 3.
Parameters Supply Voltage Input Voltage Differential Input Voltage 1 Output Short-Circuit Duration to GND Storage Temperature Range R, RM, RU, RT, UJ Packages Operating Temperature Range Junction Temperature Range R, RM, RU, RT, UJ Packages Lead Temperature Range (Soldering, 60 sec)
1
Ratings 6V GND - 0.3 V to VS- + 0.3 V 5.0 V Indefinite -65C to +150C -40C to +125C
Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Table 4. Thermal Characteristics
-65C to +150C 300C Package Type 5-Lead TSOT-23 (UJ-5) 5-Lead SOT-23 (RT-5) 8-Lead SOIC_N (R-8) 8-Lead MSOP (RM-8) 14-Lead SOIC_N (R-14) 14-Lead TSSOP (RU-14)
1
Differential input voltage is limited to 5 V or the supply voltage, whichever is less.
JA 1 207 230 158 190 105 148
JC 61 146 43 44 43 23
Unit C/W C/W C/W C/W C/W C/W
JA is specified for worst-case conditions, that is, JA is specified for the device soldered in a circuit board for surface-mount packages. This was measured using a standard 2-layer board.
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
Rev. E | Page 6 of 24
AD8628/AD8629/AD8630 TYPICAL PERFORMANCE CHARACTERISTICS
180 160 VS = 2.7V TA = 25C
100 90 80 VS = 5V VCM = 2.5V TA = 25C
NUMBER OF AMPLIFIERS
140
NUMBER OF AMPLIFIERS
02735-003
120 100 80 60 40 20 0 -2.5 -1.5 -0.5 0.5 INPUT OFFSET VOLTAGE (V) 1.5
70 60 50 40 30 20 10 0 -2.5 -1.5 -0.5 0.5 INPUT OFFSET VOLTAGE (V) 1.5
02735-006
2.5
2.5
Figure 7. Input Offset Voltage Distribution
Figure 10. Input Offset Voltage Distribution
60 VS = 5V 50 +85C
7 VS = 5V TA = -40C TO +125C
6
INPUT BIAS CURRENT (pA)
NUMBER OF AMPLIFIERS
5
40
4 3 2
30
20 +25C 10
02735-004
0 0 1 2 3 4 5 INPUT COMMON-MODE VOLTAGE (V) 6
0 0 2 4 6 TCVOS (nV/C) 8
10
Figure 8. AD8628 Input Bias Current vs. Input Common-Mode
Figure 11. Input Offset Voltage Drift
1500 VS = 5V 1000 150C
1k VS = 5V TA = 25C 100
INPUT BIAS CURRENT (pA)
500
OUTPUT VOLTAGE (mV)
125C
10 SOURCE SINK 1
0
-500
-1000
02735-005
0.1
02735-008
-1500 0 1 2 3 4 5 INPUT COMMON-MODE VOLTAGE (V) 6
0.01 0.0001
0.001
0.01 0.1 LOAD CURRENT (mA)
1
10
Figure 9. AD8628 Input Bias Current vs. Input Common-Mode Voltage at 5 V
Figure 12. Output Voltage to Supply Rail vs. Load Current
Rev. E | Page 7 of 24
02735-007
-40C
1
AD8628/AD8629/AD8630
1k VS = 2.7V 100
800 1000 TA = 25C
OUTPUT VOLTAGE (mV)
10 SOURCE SINK 1
SUPPLY CURRENT (A)
02735-009
600
400
0.1
200
02735-012
0.01 0.0001
0.001
0.01 0.1 LOAD CURRENT (mA)
1
10
0 0 1 2 3 4 SUPPLY VOLTAGE (V) 5 6
Figure 13. Output Voltage to Supply Rail vs. Load Current
Figure 16. Supply Current vs. Supply Voltage
1500 VS = 5V VCM = 2.5V TA = -40C TO +150C
60 VS = 2.7V CL = 20pF RL = M = 45 0 45 20 90 135 0 180 225
02735-010
1150
INPUT BIAS CURRENT (pA)
40
900
450
100
0 -50
-25
0
25 50 75 100 TEMPERATURE (C)
125
150
175
10k
100k 1M FREQUENCY (Hz)
10M
Figure 14. AD8628 Input Bias Current vs. Temperature
Figure 17. Open-Loop Gain and Phase vs. Frequency
1250
TA = 25C
70 60 VS = 5V CL = 20pF RL = M = 52.1 0 45 90 135 180 225
02735-014
5V 1000
50
02735-013
2.7V 750
40 30 20 10 0 -10
500
250
02735-011
-20 -30 10k 100k 1M FREQUENCY (Hz) 10M
0 -50
0
50 100 TEMPERATURE (C)
150
200
Figure 15. Supply Current vs. Temperature
Figure 18. Open-Loop Gain and Phase vs. Frequency
Rev. E | Page 8 of 24
PHASE SHIFT (Degrees)
SUPPLY CURRENT (A)
OPEN-LOOP GAIN (dB)
PHASE SHIFT (Degrees)
OPEN-LOOP GAIN (dB)
AD8628/AD8629/AD8630
70 60 50 VS = 2.7V CL = 20pF RL = 2k 300 VS = 5V 270 240
CLOSED-LOOP GAIN (dB)
40 30 20 10 0 -10 -20 -30 1k 10k 100k 1M FREQUENCY (Hz) 10M AV = 1
02735-015
OUTPUT IMPEDANCE ()
210 180 150 120 90 60 30 0 100 1k 10k 100k 1M FREQUENCY (Hz) AV = 100
AV = 100
AV = 1
AV = 10
AV = 10
02735-018
10M
100M
Figure 19. Closed-Loop Gain vs. Frequency
Figure 22. Output Impedance vs. Frequency
70 60 50 VS = 5V CL = 20pF RL = 2k
CLOSED-LOOP GAIN (dB)
40 30
VOLTAGE (500mV/DIV)
AV = 100
AV = 10 20 10 AV = 1 0 -10 -20 -30 1k 10k 100k 1M FREQUENCY (Hz) 10M
02735-016
0V
VS = 1.35V CL = 300pF RL = AV = 1
TIME (4s/DIV)
Figure 20. Closed-Loop Gain vs. Frequency
Figure 23. Large Signal Transient Response
300 VS = 2.7V 270 240
OUTPUT IMPEDANCE ()
VOLTAGE (1V/DIV)
210 180
AV = 1 AV = 100
150 120 90 60 30 0 100 1k 10k 100k 1M FREQUENCY (Hz) 10M AV = 10
02735-017
0V
VS = 2.5V CL = 300pF RL = AV = 1
100M
TIME (5s/DIV)
Figure 21. Output Impedance vs. Frequency
Figure 24. Large Signal Transient Response
Rev. E | Page 9 of 24
02735-020
02735-019
AD8628/AD8629/AD8630
80 VS = 1.35V CL = 50pF RL = AV = 1 70 60 VS = 2.5V RL = 2k TA = 25C
VOLTAGE (50mV/DIV)
OVERSHOOT (%)
50 40 30 OS- 20 OS+
0V
02735-021
0 1 10 100 CAPACITIVE LOAD (pF)
1k
TIME (4s/DIV)
Figure 25. Small Signal Transient Response
Figure 28. Small Signal Overshoot vs. Load Capacitance
VS = 2.5V CL = 50pF RL = AV = 1
VIN
VOLTAGE (50mV/DIV)
VS = 2.5V AV = -50 RL = 10k CL = 0 CH1 = 50mV/DIV CH2 = 1V/DIV
0V
VOLTAGE (V)
0V
0V
02735-022
VOUT TIME (2s/DIV)
TIME (4s/DIV)
Figure 26. Small Signal Transient Response
Figure 29. Positive Overvoltage Recovery
100 90 80 70 VS = 1.35V RL = 2k TA = 25C 0V VS = 2.5V AV = -50 RL = 10k CL = 0 CH1 = 50mV/DIV CH2 = 1V/DIV
OVERSHOOT (%)
60 50 40 30 20 10 0 1 10 100 CAPACITIVE LOAD (pF)
02735-023
OS-
VOLTAGE (V)
VIN
VOUT
OS+
1k
TIME (10s/DIV)
Figure 27. Small Signal Overshoot vs. Load Capacitance
Figure 30. Negative Overvoltage Recovery
Rev. E | Page 10 of 24
02735-026
0V
02735-025
02735-024
10
AD8628/AD8629/AD8630
VS = 2.5V VIN = 1kHz @ 3V p-p CL = 0pF RL = 10k AV = 1 140 120 100 80 VS = 1.35V
VOLTAGE (1V/DIV)
PSRR (dB)
60 +PSRR 40 20 0 -20 -PSRR
0V
02735-027
-40 -60 100 1k 10k 100k FREQUENCY (Hz) 1M
TIME (200s/DIV)
10M
Figure 31. No Phase Reversal
Figure 34. PSRR vs. Frequency
140 VS = 2.7V 120 100 80
140 120 100 80
VS = 2.5V
CMRR (dB)
PSRR (dB)
60 40 20 0 -20
02735-028
60 +PSRR 40 20 0 -20 -40 -60 100 1k 10k 100k FREQUENCY (Hz) 1M
02735-031
-PSRR
-40 -60 100 1k 10k 100k FREQUENCY (Hz) 1M
10M
10M
Figure 32. CMRR vs. Frequency
Figure 35. PSRR vs. Frequency
140 120 100 80 VS = 5V
3.0 VS = 2.7V RL = 10k TA = 25C AV = 1
2.5
OUTPUT SWING (V p-p)
2.0
CMRR (dB)
60 40 20 0 -20 -40 -60 100 1k 10k 100k FREQUENCY (Hz) 1M
02735-029
1.5
1.0
0.5
02735-032
10M
0 100
1k
10k FREQUENCY (Hz)
100k
1M
Figure 33. CMRR vs. Frequency
Figure 36. Maximum Output Swing vs. Frequency
Rev. E | Page 11 of 24
02735-030
AD8628/AD8629/AD8630
5.5 5.0 4.5 VS = 5V RL = 10k TA = 25C AV = 1 120 105 90 75 60 45 30
02735-036
VS = 2.7V NOISE AT 1kHz = 21.3nV
OUTPUT SWING (V p-p)
4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 100
VOLTAGE NOISE DENSITY (nV/Hz)
02735-033
15 0 0 0.5 1.0 1.5 FREQUENCY (kHz) 2.0
1k
10k FREQUENCY (Hz)
100k
1M
2.5
Figure 37. Maximum Output Swing vs. Frequency
Figure 40. Voltage Noise Density at 2.7 V from 0 Hz to 2.5 kHz
0.60 VS = 2.7V 0.45 0.30
120 105 90 75 60 45 30
02735-037
VS = 2.7V NOISE AT 10kHz = 42.4nV
0.15 0 -0.15 -0.30
02735-034
-0.45 -0.60 0 1 2 3 4 5 6 TIME (s) 7 8 9 10
VOLTAGE NOISE DENSITY (nV/Hz)
VOLTAGE (V)
15 0 0 5 10 15 FREQUENCY (kHz) 20 25
Figure 38. 0.1 Hz to 10 Hz Noise
Figure 41. Voltage Noise Density at 2.7 V from 0 Hz to 25 kHz
0.60 VS = 5V 0.45 0.30
120 105 90 75 60 45 30
02735-038
VS = 5V NOISE AT 1kHz = 22.1nV
0.15 0 -0.15 -0.30
02735-035
-0.45 -0.60 0 1 2 3 4 5 6 TIME (s) 7 8 9 10
VOLTAGE NOISE DENSITY (nV/Hz)
VOLTAGE (V)
15 0 0 0.5 1.0 1.5 FREQUENCY (kHz) 2.0
2.5
Figure 39. 0.1 Hz to 10 Hz Noise
Figure 42. Voltage Noise Density at 5 V from 0 Hz to 2.5 kHz
Rev. E | Page 12 of 24
AD8628/AD8629/AD8630
120 105 90 75 60 45 30
02735-039
150
OUTPUT SHORT-CIRCUIT CURRENT (mA)
VS = 5V NOISE AT 10kHz = 36.4nV
VS = 2.7V TA = -40C TO +150C 100
VOLTAGE NOISE DENSITY (nV/Hz)
50 ISC- 0 ISC+ -50
02735-042
15 0 0 5 10 15 FREQUENCY (kHz) 20 25
-100 -50
-25
0
25 50 75 100 TEMPERATURE (C)
125
150
175
Figure 43. Voltage Noise Density at 5 V from 0 Hz to 25 kHz
Figure 46. Output Short-Circuit Current vs. Temperature
120 105 90 75 60 45 30
02735-040
150
OUTPUT SHORT-CIRCUIT CURRENT (mA)
VS = 5V
VS = 5V TA = -40C TO +150C 100 ISC- 50
VOLTAGE NOISE DENSITY (nV/Hz)
0
-50 ISC+ -100 -50 -25 0 25 50 75 100 TEMPERATURE (C) 125 150
02735-043
15 0 0 5 FREQUENCY (kHz) 10
175
Figure 44. Voltage Noise
Figure 47. Output Short-Circuit Current vs. Temperature
150 140
1k VS = 5V
OUTPUT-TO-RAIL VOLTAGE (mV)
VCC - VOH @ 1k 100 VOL - VEE @ 1k VCC - VOH @ 10k 10 VOL - VEE @ 10k VCC - VOH @ 100k 1 VOL - VEE @ 100k
02735-044
POWER SUPPLY REJECTION (dB)
130 120 110 100 90 80 70 60 50 -50 -25 0 25 50 TEMPERATURE (C) 75 100
02735-041
VS = 2.7V TO 5V TA = -40C TO +125C
125
0.10 -50
-25
0
25 50 75 100 TEMPERATURE (C)
125
150
175
Figure 45. Power Supply Rejection vs. Temperature
Figure 48. Output-to-Rail Voltage vs. Temperature
Rev. E | Page 13 of 24
AD8628/AD8629/AD8630
1k VS = 2.7V
OUTPUT-TO-RAIL VOLTAGE (mV)
140 VSY = 2.5V VCC - VOH @ 1k 120
CHANNEL SEPARATION (dB)
100 VOL - VEE @ 1k VCC - VOH @ 10k 10 VOL - VEE @ 10k VCC - VOH @ 100k 1 VOL - VEE @ 100k
02735-045
100 80 R1 10k V- R2 100
60 40
+2.5V + - V+
VIN 28mV p-p
A
V- -2.5V VOUT V+
B
02735-062
20 0 1k
0.10 -50
-25
0
25 50 75 100 TEMPERATURE (C)
125
150
175
10k
100k FREQUENCY (Hz)
1M
10M
Figure 49. Output-to-Rail Voltage vs. Temperature
Figure 50. AD8629/AD8630 Channel Separation
Rev. E | Page 14 of 24
AD8628/AD8629/AD8630 FUNCTIONAL DESCRIPTION
The AD8628/AD8629/AD8630 are single-supply, ultrahigh precision rail-to-rail input and output operational amplifiers. The typical offset voltage of less than 1 V allows these amplifiers to be easily configured for high gains without risk of excessive output voltage errors. The extremely small temperature drift of 2 nV/C ensures a minimum of offset voltage error over their entire temperature range of -40C to +125C, making these amplifiers ideal for a variety of sensitive measurement applications in harsh operating environments. The AD8628/AD8629/AD8630 achieve a high degree of precision through a patented combination of auto-zeroing and chopping. This unique topology allows the AD8628/AD8629/ AD8630 to maintain their low offset voltage over a wide temperature range and over their operating lifetime. The AD8628/AD8629/AD8630 also optimize the noise and bandwidth over previous generations of auto-zero amplifiers, offering the lowest voltage noise of any auto-zero amplifier by more than 50%. Previous designs used either auto-zeroing or chopping to add precision to the specifications of an amplifier. Auto-zeroing results in low noise energy at the auto-zeroing frequency, at the expense of higher low frequency noise due to aliasing of wideband noise into the auto-zeroed frequency band. Chopping results in lower low frequency noise at the expense of larger noise energy at the chopping frequency. The AD8628/AD8629/ AD8630 family uses both auto-zeroing and chopping in a patented ping-pong arrangement to obtain lower low frequency noise together with lower energy at the chopping and autozeroing frequencies, maximizing the signal-to-noise ratio (SNR) for the majority of applications without the need for additional filtering. The relatively high clock frequency of 15 kHz simplifies filter requirements for a wide, useful, noise-free bandwidth. The AD8628 is among the few auto-zero amplifiers offered in the 5-lead TSOT-23 package. This provides a significant improvement over the ac parameters of the previous auto-zero amplifiers. The AD8628/AD8629/AD8630 have low noise over a relatively wide bandwidth (0 Hz to 10 kHz) and can be used where the highest dc precision is required. In systems with signal bandwidths of from 5 kHz to 10 kHz, the AD8628/ AD8629/AD8630 provide true 16-bit accuracy, making them the best choice for very high resolution systems.
1/f NOISE
1/f noise, also known as pink noise, is a major contributor to errors in dc-coupled measurements. This 1/f noise error term can be in the range of several V or more, and, when amplified with the closed-loop gain of the circuit, can show up as a large output offset. For example, when an amplifier with a 5 V p-p 1/f noise is configured for a gain of 1,000, its output has 5 mV of error due to the 1/f noise. But the AD8628/AD8629/AD8630 eliminate 1/f noise internally, and thereby greatly reduce output errors. The internal elimination of 1/f noise is accomplished as follows. 1/f noise appears as a slowly varying offset to AD8628/AD8629/ AD8630 inputs. Auto-zeroing corrects any dc or low frequency offset. Therefore, the 1/f noise component is essentially removed, leaving the AD8628/AD8629/AD8630 free of 1/f noise. One of the biggest advantages that the AD8628/AD8629/ AD8630 bring to systems applications over competitive autozero amplifiers is their very low noise. The comparison shown in Figure 51 indicates an input-referred noise density of 19.4 nV/Hz at 1 kHz for the AD8628, which is much better than the LTC2050 and LMC2001. The noise is flat from dc to 1.5 kHz, slowly increasing up to 20 kHz. The lower noise at low frequency is desirable where auto-zero amplifiers are widely used.
120 105 90 75 60 45 30
02735-046
VOLTAGE NOISE DENSITY (nV/Hz)
LTC2050 (89.7nV/Hz)
LMC2001 (31.1nV/Hz)
15 0 0
AD8628 (19.4nV/Hz) 2
MK AT 1kHz FOR ALL 3 GRAPHS 4 6 FREQUENCY (kHz) 8 10
12
Figure 51. Noise Spectral Density of AD8628 vs. Competition
Rev. E | Page 15 of 24
AD8628/AD8629/AD8630
PEAK-TO-PEAK NOISE
Because of the ping-pong action between auto-zeroing and chopping, the peak-to-peak noise of the AD8628/AD8629/AD8630 is much lower than the competition. Figure 52 and Figure 53 show this comparison.
en p-p = 0.5V BW = 0.1Hz TO 10Hz 50 45 40 35
NOISE (dB)
30 25 20 15
VOLTAGE (0.5V/DIV)
10 5 0 0 10 20 30 40 50 60 70 FREQUENCY (kHz) 80 90
02735-050
100
Figure 55. Simulation Transfer Function of the Test Circuit
02735-047
50 45 40 35
TIME (1s/DIV)
Figure 52. AD8628 Peak-to-Peak Noise
NOISE (dB)
30 25 20 15 10 5 0 0 10 20 30 40 50 60 70 FREQUENCY (kHz) 80 90
02735-051
en p-p = 2.3V BW = 0.1Hz TO 10Hz
VOLTAGE (0.5V/DIV)
100
Figure 56. Actual Transfer Function of the Test Circuit
The measured noise spectrum of the test circuit charted in Figure 56 shows that noise between 5 kHz and 45 kHz is successfully rolled off by the first-order filter.
TIME (1s/DIV)
02735-048
Figure 53. LTC2050 Peak-to-Peak Noise
NOISE BEHAVIOR WITH FIRST-ORDER LOW-PASS FILTER
The AD8628 was simulated as a low-pass filter (Figure 55) and then configured as shown in Figure 54. The behavior of the AD8628 matches the simulated data. It was verified that noise is rolled off by first-order filtering. Figure 55 and Figure 56 show the difference between the simulated and actual transfer functions of the circuit shown in Figure 54.
TOTAL INTEGRATED INPUT-REFERRED NOISE FOR FIRST-ORDER FILTER
For a first-order filter, the total integrated noise from the AD8628 is lower than the LTC2050.
10
LTC2050
RMS NOISE (V)
AD8551 1
AD8628
IN OUT 100k 470pF
1k
02735-049
0.1 10
Figure 54. Test Circuit: First-Order Low-Pass Filter, x101 Gain and 3 kHz Corner Frequency
Rev. E | Page 16 of 24
100 1k 3dB FILTER BANDWIDTH (Hz)
10k
Figure 57. 3 dB Filter Bandwidth in Hz
02735-052
AD8628/AD8629/AD8630
INPUT OVERVOLTAGE PROTECTION
Although the AD8628/AD8629/AD8630 are rail-to-rail input amplifiers, care should be taken to ensure that the potential difference between the inputs does not exceed the supply voltage. Under normal negative feedback operating conditions, the amplifier corrects its output to ensure that the two inputs are at the same voltage. However, if either input exceeds either supply rail by more than 0.3 V, large currents begin to flow through the ESD protection diodes in the amplifier. These diodes are connected between the inputs and each supply rail to protect the input transistors against an electrostatic discharge event, and they are normally reverse-biased. However, if the input voltage exceeds the supply voltage, these ESD diodes can become forward-biased. Without current limiting, excessive amounts of current could flow through these diodes, causing permanent damage to the device. If inputs are subject to overvoltage, appropriate series resistors should be inserted to limit the diode current to less than 5 mA maximum.
VOLTAGE (V)
VIN CH1 = 50mV/DIV CH2 = 1V/DIV AV = -50
VOLTAGE (V)
0V
0V
VOUT TIME (500s/DIV)
Figure 58. Positive Input Overload Recovery for the AD8628
VIN
CH1 = 50mV/DIV CH2 = 1V/DIV AV = -50
OUTPUT PHASE REVERSAL
Output phase reversal occurs in some amplifiers when the input common-mode voltage range is exceeded. As common-mode voltage is moved outside of the common-mode range, the outputs of these amplifiers can suddenly jump in the opposite direction to the supply rail. This is the result of the differential input pair shutting down, causing a radical shifting of internal voltages that results in the erratic output behavior. The AD8628/AD8629/AD8630 amplifiers have been carefully designed to prevent any output phase reversal, provided that both inputs are maintained within the supply voltages. If one or both inputs could exceed either supply voltage, a resistor should be placed in series with the input to limit the current to less than 5 mA. This ensures that the output does not reverse its phase.
0V
0V
VOUT TIME (500s/DIV)
Figure 59. Positive Input Overload Recovery for LTC2050
VIN
CH1 = 50mV/DIV CH2 = 1V/DIV AV = -50
OVERLOAD RECOVERY TIME
Many auto-zero amplifiers are plagued by a long overload recovery time, often in ms, due to the complicated settling behavior of the internal nulling loops after saturation of the outputs. The AD8628/AD8629/AD8630 have been designed so that internal settling occurs within two clock cycles after output saturation happens. This results in a much shorter recovery time, less than 10 s, when compared to other auto-zero amplifiers. The wide bandwidth of the AD8628/AD8629/ AD8630 enhances performance when the parts are used to drive loads that inject transients into the outputs. This is a common situation when an amplifier is used to drive the input of switched capacitor ADCs.
VOLTAGE (V)
0V
0V
VOUT
TIME (500s/DIV)
Figure 60. Positive Input Overload Recovery for LMC2001
Rev. E | Page 17 of 24
02735-055
02735-054
02735-053
AD8628/AD8629/AD8630
0V CH1 = 50mV/DIV CH2 = 1V/DIV AV = -50
The results shown in Figure 58 to Figure 63 are summarized in Table 5. Table 5. Overload Recovery Time
Product AD8628 LTC2050 LMC2001 Positive Overload Recovery (s) 6 650 40,000 Negative Overload Recovery (s) 9 25,000 35,000
VOLTAGE (V)
VIN
VOUT
02735-056
0V
INFRARED SENSORS
Infrared (IR) sensors, particularly thermopiles, are increasingly being used in temperature measurement for applications as wide-ranging as automotive climate control, human ear thermometers, home insulation analysis, and automotive repair diagnostics. The relatively small output signal of the sensor demands high gain with very low offset voltage and drift to avoid dc errors. If interstage ac coupling is used, as in Figure 64, low offset and drift prevent the input amplifier's output from drifting close to saturation. The low input bias currents generate minimal errors from the sensor's output impedance. As with pressure sensors, the very low amplifier drift with time and temperature eliminate additional errors once the temperature measurement is calibrated. The low 1/f noise improves SNR for dc measurements taken over periods often exceeding one-fifth of a second. Figure 64 shows a circuit that can amplify ac signals from 100 V to 300 V up to the 1 V to 3 V levels, with gain of 10,000 for accurate A/D conversion.
10k 100 100k 5V 5V 100k
TIME (500s/DIV)
Figure 61. Negative Input Overload Recovery for the AD8628
0V CH1 = 50mV/DIV CH2 = 1V/DIV AV = -50 VIN VOUT
VOLTAGE (V)
0V
TIME (500s/DIV)
Figure 62. Negative Input Overload Recovery for LTC2050
0V CH1 = 50mV/DIV CH2 = 1V/DIV AV = -50
02735-057
100V - 300V IR DETECTOR
10F
VOLTAGE (V)
VIN VOUT
1/2 AD8629
10k fC 1.6Hz TO BIAS VOLTAGE
1/2 AD8629
Figure 64. AD8629 Used as Preamplifier for Thermopile
02735-058
0V
TIME (500s/DIV)
Figure 63. Negative Input Overload Recovery for LMC2001
Rev. E | Page 18 of 24
02735-059
AD8628/AD8629/AD8630
PRECISION CURRENT SHUNT SENSOR
A precision current shunt sensor benefits from the unique attributes of auto-zero amplifiers when used in a differencing configuration, as shown in Figure 65. Current shunt sensors are used in precision current sources for feedback control systems. They are also used in a variety of other applications, including battery fuel gauging, laser diode power measurement and control, torque feedback controls in electric power steering, and precision power metering.
SUPPLY 100k e = 1,000 RS I 100mV/mA RS 0.1 RL
OUTPUT AMPLIFIER FOR HIGH PRECISION DACS
The AD8628/AD8629/AD8360 are used as output amplifiers for a 16-bit high precision DAC in a unipolar configuration. In this case, the selected op amp needs to have very low offset voltage (the DAC LSB is 38 V when operated with a 2.5 V reference) to eliminate the need for output offset trims. Input bias current (typically a few tens of picoamperes) must also be very low, because it generates an additional zero code error when multiplied by the DAC output impedance (approximately 6 k). Rail-to-rail input and output provide full-scale output with very little error. Output impedance of the DAC is constant and codeindependent, but the high input impedance of the AD8628/ AD8629/AD8630 minimizes gain errors. The amplifiers' wide bandwidth also serves well in this case. The amplifiers, with settling time of 1 s, add another time constant to the system, increasing the settling time of the output. The settling time of the AD5541 is 1 s. The combined settling time is approximately 1.4 s, as can be derived from the following equation:
t S (TOTAL ) =
I 100
C 5V
AD8628
100k 100
02735-060
C
Figure 65. Low-Side Current Sensing
(t S DAC )2 + (t S AD8628)2
2.5V 10F
In such applications, it is desirable to use a shunt with very low resistance to minimize the series voltage drop; this minimizes wasted power and allows the measurement of high currents while saving power. A typical shunt might be 0.1 . At measured current values of 1 A, the shunt's output signal is hundreds of mV, or even V, and amplifier error sources are not critical. However, at low measured current values in the 1 mA range, the 100 V output voltage of the shunt demands a very low offset voltage and drift to maintain absolute accuracy. Low input bias currents are also needed, so that injected bias current does not become a significant percentage of the measured current. High open-loop gain, CMRR, and PSRR help to maintain the overall circuit accuracy. As long as the rate of change of the current is not too fast, an auto-zero amplifier can be used with excellent results.
5V
0.1F
0.1F
SERIAL INTERFACE
VDD CS DIN SCLK LDAC*
REF(REF*)
REFS*
AD5541/AD5542
OUT
UNIPOLAR OUTPUT
AD8628
DGND AGND
03023-061
*AD5542 ONLY
Figure 66. AD8628 Used as an Output Amplifier
Rev. E | Page 19 of 24
AD8628/AD8629/AD8630 OUTLINE DIMENSIONS
2.90 BSC
5.00 (0.1968) 4.80 (0.1890)
4
8 5 4
5
1.60 BSC
1 2 3
2.80 BSC
4.00 (0.1574) 3.80 (0.1497) 1
6.20 (0.2440) 5.80 (0.2284)
PIN 1 0.95 BSC *0.90 0.87 0.84 1.90 BSC
0.25 (0.0098) 0.10 (0.0040)
1.27 (0.0500) BSC
1.75 (0.0688) 1.35 (0.0532)
0.50 (0.0196) x 45 0.25 (0.0099)
*1.00 MAX
0.20 0.08 8 4 0 0.60 0.45 0.30
0.51 (0.0201) COPLANARITY SEATING 0.31 (0.0122) 0.10 PLANE
8 0.25 (0.0098) 0 1.27 (0.0500) 0.40 (0.0157) 0.17 (0.0067)
0.10 MAX
0.50 0.30
SEATING PLANE
COMPLIANT TO JEDEC STANDARDS MS-012AA CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
*COMPLIANT TO JEDEC STANDARDS MO-193-AB WITH THE EXCEPTION OF PACKAGE HEIGHT AND THICKNESS.
Figure 67. 5-Lead Thin Small Outline Transistor Package [TSOT] (UJ-5) Dimensions shown in millimeters
Figure 69. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches)
3.00 BSC
2.90 BSC
5
4
8
5
1.60 BSC
1
2.80 BSC
2 3
3.00 BSC
1
4.90 BSC
4
PIN 1 0.95 BSC 1.30 1.15 0.90 1.90 BSC
0.15 0.00
PIN 1 0.65 BSC 1.10 MAX 8 0 0.80 0.60 0.40
1.45 MAX
0.22 0.08 10 5 0 0.60 0.45 0.30
0.15 MAX
0.50 0.30
0.38 0.22 COPLANARITY 0.10
0.23 0.08 SEATING PLANE
SEATING PLANE
COMPLIANT TO JEDEC STANDARDS MO-187AA
COMPLIANT TO JEDEC STANDARDS MO-178AA
Figure 68. 5-Lead Small Outline Transistor Package [SOT-23] (RT-5) Dimensions shown in millimeters
Figure 70. 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters
Rev. E | Page 20 of 24
AD8628/AD8629/AD8630
8.75 (0.3445) 8.55 (0.3366)
14 1 8 7
5.10 5.00 4.90
4.00 (0.1575) 3.80 (0.1496)
6.20 (0.2441) 5.80 (0.2283)
4.50 4.40 4.30
14
8
0.25 (0.0098) 0.10 (0.0039) COPLANARITY 0.10
1.27 (0.0500) BSC
6.40 BSC
1 7
1.75 (0.0689) 1.35 (0.0531)
0.50 (0.0197) x 45 0.25 (0.0098)
0.51 (0.0201) 0.31 (0.0122)
SEATING PLANE
8 0.25 (0.0098) 0 1.27 (0.0500) 0.40 (0.0157) 0.17 (0.0067)
PIN 1 1.05 1.00 0.80 0.65 BSC 1.20 MAX 0.15 0.05 0.30 0.19 0.20 0.09 8 0 0.75 0.60 0.45
COMPLIANT TO JEDEC STANDARDS MS-012AB CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
SEATING COPLANARITY PLANE 0.10
COMPLIANT TO JEDEC STANDARDS MO-153AB-1
Figure 71. 14-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-14) Dimensions shown in millimeters and (inches)
Figure 72. 14-Lead Thin Shrink Small Outline Package [TSSOP] (RU-14) Dimensions shown in millimeters
Rev. E | Page 21 of 24
AD8628/AD8629/AD8630
ORDERING GUIDE
Model AD8628AUJ-R2 AD8628AUJ-REEL AD8628AUJ-REEL7 AD8628AUJZ-R2 1 AD8628AUJZ-REEL1 AD8628AUJZ-REEL71 AD8628AR AD8628AR-REEL AD8628AR-REEL7 AD8628ARZ1 AD8628ARZ-REEL1 AD8628ARZ-REEL71 AD8628ART-R2 AD8628ART-REEL7 AD8628ARTZ-R21 AD8628ARTZ-REEL71 AD8629ARZ1 AD8629ARZ-REEL1 AD8629ARZ-REEL71 AD8629ARMZ-R21 AD8629ARMZ-REEL1 AD8630ARUZ1 AD8630ARUZ-REEL1 AD8630ARZ1 AD8630ARZ-REEL1 AD8630ARZ-REEL71
1
Temperature Range -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C
Package Description 5-Lead TSOT-23 5-Lead TSOT-23 5-Lead TSOT-23 5-Lead TSOT-23 5-Lead TSOT-23 5-Lead TSOT-23 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 5-Lead SOT-23 5-Lead SOT-23 5-Lead SOT-23 5-Lead SOT-23 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead MSOP 8-Lead MSOP 14-Lead TSSOP 14-Lead TSSOP 14-Lead SOIC_N 14-Lead SOIC_N 14-Lead SOIC_N
Package Option UJ-5 UJ-5 UJ-5 UJ-5 UJ-5 UJ-5 R-8 R-8 R-8 R-8 R-8 R-8 RT-5 RT-5 RT-5 RT-5 R-8 R-8 R-8 RM-8 RM-8 RU-14 RU-14 R-14 R-14 R-14
Branding AYB AYB AYB A0L A0L A0L
AYA AYA A0L A0L
A06 A06
Z = Pb-free part.
Rev. E | Page 22 of 24
AD8628/AD8629/AD8630 NOTES
Rev. E | Page 23 of 24
AD8628/AD8629/AD8630 NOTES
(c)2005 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. C02735-0-5/05(E)
Rev. E | Page 24 of 24

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